A clamping device of the type described in the introduction is known from EP 0 391 346 B1. The clearances continue over the length of the guide shoe and form a constituent part of a T-slot-shaped cross-sectional configuration. The clamping claw is of a curved configuration, in which the free ends of the bracing leg and of the clamping leg are arranged at a higher level than the continuations which engage directly into the clearances. The continuations are of an approximately elliptical cross-section with the major axis being aligned approximately in the longitudinal direction of the clamping claw. The clamping claw has a return spring which acts counter to the clamping direction, is supported on the guide shoe and also fulfils the function of fixing the clamping claw after displacement in the guide shoe. All that is provided for fastening the guide shoe on the clamping table is a fastening bolt which as a rule, is assigned a sliding block. The fastening bolt can be inserted into one or more through-passages arranged in the front region of the guide shoe. It is thus possible to clamp any point of a workpiece onto a clamping table in a space around the clamping device. The clamping claw can be displaced in a stepless manner in the guide shoe in the longitudinal direction and fixed in the clamping position. In a vertical direction, a correspondingly large vertical region of workpieces of different heights can be clamped, it being possible optionally to clamp into the guide shoe clamping claws which are bent in different manners. The displacement of the clamping claw in the horizontal direction relative to the guide shoe is restricted on paths in which the continuations engaging into the clearances are still located securely in guide shoes. The disadvantage with this clamping device is that the displacement path of the clamping claw in the guide shoe is restricted. The result of this is that it is possible to clamp a workpiece only in its border region and, in the direction of its central region, only in a length corresponding to the bracing leg. In the case of clamping heights of different sizes, clamping claws which are bent in different manners have to be kept in stock and combined with the guide shoe. This involves a high degree of outlay and does not make it any easier, for example, to clamp a workpiece in machining positions at different heights. Linear contact takes place between the elliptical continuations and the T-slot-shaped clearances, with the result that it is necessary to design, in particular, the side walls of the guide shoe to be very thick. The floor of the guide shoe too is of a relatively great thickness. It is configured in a continuous manner because the clamping bolt can be supported on the continuous floor step solder in each clamping position. This results in the weight of the guide shoe being relatively great.
DE 28 08 667 A1 discloses a clamping device for a machine tool, of which the guide shoe does not exhibit a planar continuous bearing surface for mounting on a clamping table, but in which a single fastening bolt engages in the guide shoe in an elevated position. In order to clamp particularly high workpieces, provision is made for a foot and an intermediate block which are assigned to the guide shoe and are matched to the same.
These three differently designed parts are correspondingly stacked one upon the other and fastened on one another, with the result that relatively high clamping heights can then be provided for.
The object of the invention is to develop further a clamping device of the type described in the introduction such that, by means of the clamping claw, a wider range of clamping positions can be covered in the horizontal direction or, in other words, it is possible to span workpieces with more widely variable clamping positions, starting with the clamping of just a border region of the workpiece and continuing, to a certain extent, into the central region of the workpiece.